diff --git a/docs/source/user_guide.rst b/docs/source/user_guide.rst index 144df3b1..0a18b073 100644 --- a/docs/source/user_guide.rst +++ b/docs/source/user_guide.rst @@ -51,10 +51,139 @@ you can be assured you are on target! of the first time set-up items in the Quick Start +Power & Charging +===================================== + +PiFinders ordered with the optional internal battery will run for an evening on a single +charge, and you can keep one going indefinitely from any USB-C power source. This section +covers how the two USB-C ports differ, how charging behaves, how long a charge lasts, and +how to look after the battery. For the very first power-on, the :ref:`quick_start:powering the pifinder` +section of the Quick Start walks through it step by step. + +The two USB-C ports +------------------- + +A battery-equipped PiFinder has two USB-C ports on top of the unit, and they do different +things: + +.. image:: images/quick_start/power.jpeg + +- The port nearest the **back** of the case (marked with the arrow above) both powers the + PiFinder **and** charges the internal battery. This is the one to use for charging. +- The port nearest the **keypad** powers the unit only — it does not charge the battery. + It is also wired ahead of the power switch, so plugging into it turns the PiFinder on + immediately *regardless of the switch position*. + +During an observing session the keypad-side (power-only) port is the nicer one to run from, +because the charging port's indicator LED is quite bright in the dark. A unit without the +internal battery has only the single power-only port. + +The power switch is the small white **slide** switch on top of the unit, above the screen +(highlighted with a box in the image above). Facing the screen, slide it right for on and +left for off. It is a switch, not a button. + +Charging +-------- + +Plug a USB-C cable into the charging port (nearest the back). The indicator LED glows +**blue** while charging and turns **green** when the battery is full. From empty, a full +charge takes roughly three hours, though this varies a good deal with the power source — +a Power Delivery (PD) charger negotiates more power and fills faster, while a basic 5V +supply charges more slowly but works fine. + +Charge with the power switch in the **off** position. If the PiFinder is running while +plugged in, it can draw about as much current as the charger supplies, so the battery may +barely fill. A long charge that leaves the battery still flat almost always means the unit +was switched on the whole time. + +.. note:: + The last stretch of charging is slow. As the battery approaches full the charging + current tapers off, so the change from blue to green can take a while even though the + battery is nearly there. This is normal and not a fault. + +Battery life +------------ + +The internal battery runs the PiFinder for about **four to five hours**, but real runtime +depends heavily on how hard you work it. Sitting at the eyepiece on one object, or stepping +away from the scope, lets the PiFinder drop into power-save mode and stretches the time +considerably. A fast tour through many objects — with the camera, motion sensor, and screen +all busy — draws more power and shortens it. + +There is **no battery-level indicator** on the screen and no low-battery warning: when the +charge is depleted the PiFinder simply shuts off. For a long night, top up beforehand and +keep a USB-C power bank handy. You can plug external power in at any time without restarting +(see below). + +.. note:: + The PiFinder drops into power-save mode after it has been idle for a while, dimming the + screen and slowing the camera to save power. Any button press or movement of the scope + wakes it. The idle time can be changed, or turned off entirely, in the + :ref:`user_guide:settings menu`. + +Running on external power +------------------------- + +Any USB-C power source rated for at least **2A** will run the PiFinder — a wall charger, a +USB power bank, or a portable power station's USB output. As a rough guide, about +1,000mAh of power-bank capacity runs the PiFinder for an hour, so a 10,000mAh bank is good +for the better part of a night. + +External power can be plugged in mid-session without a restart. A useful trick for +stretching a long night: plug a power bank into the power-only port, then switch the battery +**off**. The PiFinder keeps running on the external power while the internal battery is held +in reserve for after the bank is unplugged. + +If you experience power dropouts, suspect the cable first — some USB-C cables are unreliable +at the ~2A the PiFinder draws, especially on long runs. + +.. warning:: + Feed the PiFinder **5V USB-C power only**. If you want to run it from a telescope's 12V + supply, you must use a 12V-to-5V step-down (DC-DC) converter with a USB-C output. Never + connect 12V directly to the PiFinder — doing so will damage it. + +Battery safety & care +--------------------- + +The internal battery is a lithium-polymer (LiPo) cell. Treated sensibly it will last for +years, but like any lithium battery it deserves a little respect. + +.. warning:: + Stop using the battery and disconnect power if it ever becomes **swollen, damaged, + unusually hot, or develops an odour**. A puffed-up or punctured LiPo cell can vent or + catch fire. Do not continue to charge or use a cell in this condition — contact us about + a replacement. + +.. warning:: + Do not **puncture, crush, drop, or open** the battery, and do not attempt to disassemble + the PiSugar power board it sits on. Keep the unit dry; the battery and electronics are + not waterproof. + +A few habits that keep the cell healthy: + +- **Charge from the built-in port only.** The PiSugar power board manages charging for you; + just supply 5V USB-C as described above. There is no need for an external LiPo charger, + and you should not connect one. +- **Charge where you can keep an eye on it,** and not on or near anything flammable. Avoid + charging or leaving the unit in extreme heat — a closed car on a sunny day is the classic + way to cook a battery. +- **Mind the temperature.** The PiFinder has been used from about -15°C (5°F) to 40°C + (100°F). Capacity drops in the cold, though the computer's own heat keeps the cell warm + enough to work in most conditions. Avoid charging a battery that is below freezing. +- **For long-term storage,** leave the cell partly charged rather than full or empty and keep + it somewhere cool and dry. Top it up every few months so it does not discharge completely. +- **Dispose of it responsibly.** A worn-out lithium battery should go to a battery-recycling + drop-off, not the household rubbish. + +.. note:: + If you ever need to replace the battery, the only compatible part is the **PiSugar S Plus + 5000mAh**. Other PiSugar models share the I2C bus with the PiFinder's motion sensor and + will cause problems, so make sure you fit the S Plus. + Adjusting Brightness ===================================== -The PiFinder is designed to allow you to adjust the brightness of the screen and keypad at any +The PiFinder is designed to allow you to adjust the brightness of the screen and keypad at any time: simply hold down the **SQUARE** button and push **+** for brighter, or **-** for dimmer. In a dark sky site, you can turn the brightness down to preserve your dark-adapted vision.